UNSW team brews espresso with ultrasound, saving energy

Scientists at the University of New South Wales (UNSW) Sydney have developed a method to brew espresso-strength coffee using ultrasonic sound waves instead of hot water, a process that could dramatically reduce the energy required for coffee production. The research, published in the Journal of Food Engineering, demonstrates that the technique can produce a concentrated coffee in under three minutes at room temperature, with blind taste tests showing participants could not reliably distinguish it from conventionally brewed espresso.

Led by Dr. Francisco Trujillo from UNSW's School of Chemical Engineering, the team converted a standard espresso machine filter basket into an ultrasonic reactor. A device called a transducer attaches to the basket, generating high-frequency sound waves that vibrate through both the coffee grounds and water. This triggers a process known as acoustic cavitation, where microscopic bubbles rapidly form and collapse against the coffee particles. The imploding bubbles act like tiny jets, fracturing the grounds and forcing flavor compounds, oils, and caffeine into the water.

The researchers spent considerable time optimizing variables such as the...